(LiNi0.5Co0.2Mn0.3O2 + AC)/graphite hybrid energy storage device with high specific energy and high rate capability

Abstract In this work, we have fabricated a novel hybrid electrochemical energy storage device with composite cathode containing LiNi 0.5 Co 0.2 Mn 0.3 O 2 and activated carbon (AC), and graphite anode. The specific energy increases with the content of LiNi 0.5 Co 0.2 Mn 0.3 O 2 in composite cathode. The hybrid device possesses a specific energy 5.7 times higher than that of the electrical double layer capacitor. Meanwhile, the hybrid device can deliver 62.6% and 42.1% of its capacity at the rate of 30C and 50C, respectively. A 107.8-mAh hybrid device has been assembled, and the specific energy of 36.2 Wh kg −1 can be achieved at an average specific power of 39.1 W kg −1 , even 8.9 Wh kg −1 at 2380 W kg −1 . Combining the high specific energy with the high power capability, the (LiNi 0.5 Co 0.2 Mn 0.3 O 2  + AC)/graphite hybrid system has demonstrated high performances for electrochemical energy storage applications.